Showing papers by "Julio Camargo published in 2020"
TL;DR: The FRIPON project as discussed by the authors is a fully automated camera and radio network deployed over a significant fraction of western Europe and a small fraction of Canada, which consists of 150 cameras and 25 European radio receivers and covers an area of about 1.5 × 106km2.
Abstract: Context. Until recently, camera networks designed for monitoring fireballs worldwide were not fully automated, implying that in case of a meteorite fall, the recovery campaign was rarely immediate. This was an important limiting factor as the most fragile - hence precious - meteorites must be recovered rapidly to avoid their alteration. Aims. The Fireball Recovery and InterPlanetary Observation Network (FRIPON) scientific project was designed to overcome this limitation. This network comprises a fully automated camera and radio network deployed over a significant fraction of western Europe and a small fraction of Canada. As of today, it consists of 150 cameras and 25 European radio receivers and covers an area of about 1.5 × 106km2. Methods. The FRIPON network, fully operational since 2018, has been monitoring meteoroid entries since 2016, thereby allowing the characterization of their dynamical and physical properties. In addition, the level of automation of the network makes it possible to trigger a meteorite recovery campaign only a few hours after it reaches the surface of the Earth. Recovery campaigns are only organized for meteorites with final masses estimated of at least 500 g, which is about one event per year in France. No recovery campaign is organized in the case of smaller final masses on the order of 50 to 100 g, which happens about three times a year; instead, the information is delivered to the local media so that it can reach the inhabitants living in the vicinity of the fall. Results. Nearly 4000 meteoroids have been detected so far and characterized by FRIPON. The distribution of their orbits appears to be bimodal, with a cometary population and a main belt population. Sporadic meteors amount to about 55% of all meteors. A first estimate of the absolute meteoroid flux (mag < -5; meteoroid size ≥∼1 cm) amounts to 1250/yr/106km2. This value is compatible with previous estimates. Finally, the first meteorite was recovered in Italy (Cavezzo, January 2020) thanks to the PRISMA network, a component of the FRIPON science project.
35 citations
TL;DR: Most of the aspects involved in the complex process to successfully observe occultations are reviewed, and some of the lessons learned may allow an increase in the success rate and scientific output of the occultation technique applied to TNOs, in the short-term future.
Abstract: In terms of scientific output, the best way to study solar system bodies is sending spacecraft to make in situ measurements or to observe at close distance. Probably, the second best means to learn about important physical properties of solar system objects is through stellar occultations. By combining occultation observations from several sites, size and shape can be derived with kilometric accuracy. Also, atmospheric properties can be derived if the body has an atmosphere. Furthermore, the technique can detect rings and even satellites (although rarely) around the main body. Except for the very special cases of Pluto and Charon, stellar occultations by Trans-Neptunian Objects (TNOs) had never been observed until October 2009. This was because the ephemeris of the TNOs have much larger uncertainties than their angular diameters (typically of the order of ∼10 milliarcsecond) and also because stellar catalogs were not accurate to the milliarcsecond level. Despite the difficulties, at the time of this writing, 43 occultations by 22 different TNOs, and 17 occultations by 5 Centaurs have been detected thanks to the efforts of several teams. Due to the complications of accurately predicting and observing these events, most of the successes have been achieved through wide international collaboration, which is a key issue to succeed in observing stellar occultations by TNOs. Multichord occultations are typically detected at a rate of ∼3 per year on average, whereas the majority of the observed occultations are single-chord detections, which means that only one site detects the occultation. In these cases, no tight constraints on size and shape can be derived from those observations alone. Here we review most of the aspects involved in the complex process to successfully observe occultations, and present some of the lessons learned. There are good prospects for the future if we take advantage of the stellar catalog from the Gaia Data Release 2 (DR2) and if we take advantage of dedicated observational programs of TNOs, to improve their orbits to the required level of accuracy, which is a critical aspect. All this, in combination with large and optimized telescope networks, may allow an increase in the success rate and scientific output of the occultation technique applied to TNOs, in the short-term future.
20 citations
01 Jan 2020
15 citations
Paris Observatory1, Paris Diderot University2, Spanish National Research Council3, University of Paris4, Institut Polytechnique des Sciences Avancées5, Centre national de la recherche scientifique6, College of Southern Idaho7, Southwest Research Institute8, University of Colorado Boulder9, Federal University of Rio de Janeiro10, Sao Paulo State University11, Federal University of Technology - Paraná12, California Polytechnic State University13, Ponta Grossa State University14
TL;DR: The first recorded stellar occultation by the large trans-Neptunian object (174567) Varda was observed on September 10, 2018 as discussed by the authors, where the authors determined the size and albedo of the object and constrain its 3D shape and density.
Abstract: We present results from the first recorded stellar occultation by the large trans-Neptunian object (174567) Varda that was observed on September 10$^{\rm th}$, 2018. Varda belongs to the high-inclination dynamically excited population, and has a satellite, Ilmare, which is half the size of Varda. We determine the size and albedo of Varda and constrain its 3D shape and density. Thirteen different sites in the USA monitored the event, five of which detected an occultation by the main body. A best-fitting ellipse to the occultation chords provides the instantaneous limb of the body, from which the geometric albedo is computed. The size and shape of Varda are evaluated, and its bulk density is constrained, using Varda's mass known from previous works. The best-fitting elliptical limb has semi-major (equatorial) axis of $(381 \pm 3)$km and an apparent oblateness $0.043\pm0.036$ corresponding to an apparent area-equivalent radius $R'_{\rm equiv}= (373\pm8)$km and geometric albedo $p_v=0.097\pm 0.004$ assuming a visual absolute magnitude $H_V=3.81\pm0.01$. Using three possible rotational periods for the body (4.76~h, 5.91~h, and 7.87~h), we derive corresponding MacLaurin solutions. Furthermore, given the low-amplitude ($0.06\pm0.01$) mag of the single-peaked rotational light-curve for the aforementioned periods, we consider the double periods. For the 5.91~h period (the most probable) and its double (11.82~h), we find bulk densities and true oblateness of $\rho=(1.52\pm0.05)$ g cm$^{-3}$, $\epsilon=0.232\pm0.036$ and $\rho=(1.25\pm0.04)$ g cm$^{-3}$, $\epsilon=0.079\pm0.044$. However, it must be noted that the other solutions cannot be excluded just yet.
14 citations
TL;DR: In this paper, the authors obtained 12 positive occultation chords from Italy, France, Slovenia and Switzerland and used them to obtain an accurate elliptical fit to the instantaneous projection of the trans-Neptunian body, compatible with the near misses.
Abstract: On 28th January 2018, the large Trans-Neptunian Object (TNO) 2002TC302 occulted a m$_v= $15.3 star with ID 130957813463146112 in the Gaia DR2 stellar catalog. 12 positive occultation chords were obtained from Italy, France, Slovenia and Switzerland. Also, 4 negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto, in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body, compatible with the near misses, can be obtained. The resulting ellipse has major and minor axes of 543 $\pm$ 18 km and 460 $\pm$ 11 km, respectively, with a position angle of 3 $\pm$ 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5m telescope at Sierra Nevada Observatory and the 1.23m telescope at Calar Alto observatory, allows us to derive possible 3D shapes and density estimations for the body, based on hydrostatic equilibrium assumptions. The effective area equivalent diameter is $\sim$ 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to $\sim$ 300 km in diameter, to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with H$_V$ measurements we derive a geometric albedo of 0.147 $\pm$ 0.005, which would be somewhat smaller if 2002TC302 has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere.
13 citations
Paris Diderot University1, Université de Namur2, Spanish National Research Council3, University of Paris4, Institut Polytechnique des Sciences Avancées5, Centre national de la recherche scientifique6, College of Southern Idaho7, Southwest Research Institute8, University of Colorado Boulder9, Federal University of Rio de Janeiro10, Sao Paulo State University11, Federal University of Technology - Paraná12, California Polytechnic State University13, Ponta Grossa State University14
TL;DR: In this article, a best-fitting ellipse to the occultation chords provides the instantaneous limb of the body, from which the geometric albedo is computed, and its bulk density is constrained using Varda's mass as known from previous works.
Abstract: Context. We present results from the first recorded stellar occultation by the large trans-Neptunian object (174567) Varda that was observed on September 10, 2018. Varda belongs to the high-inclination dynamically excited population, and has a satellite, Ilmare, which is half the size of Varda.Aims. We determine the size and albedo of Varda and constrain its 3D shape and density.Methods. Thirteen different sites in the USA monitored the event, five of which detected an occultation by the main body. A best-fitting ellipse to the occultation chords provides the instantaneous limb of the body, from which the geometric albedo is computed. The size and shape of Varda are evaluated, and its bulk density is constrained using Varda’s mass as is known from previous works.Results. The best-fitting elliptical limb has semi-major (equatorial) axis of (383 ± 3) km and an apparent oblateness of 0.066 ± 0.047, corresponding to an apparent area-equivalent radius R′equiv = (370±7) km and geometric albedo pv = 0.099 ± 0.002 assuming a visual absolute magnitude HV = 3.81 ± 0.01. Using three possible rotational periods for the body (4.76, 5.91, and 7.87 h), we derive corresponding MacLaurin solutions. Furthermore, given the low-amplitude (0.06 ± 0.01) mag of the single-peaked rotational light-curve for the aforementioned periods, we consider the double periods. For the 5.91 h period (the most probable) and its double (11.82 h), we find bulk densities and true oblateness of ρ = (1.78 ± 0.06) g cm−3, ɛ = 0.235 ± 0.050, and ρ = (1.23 ± 0.04) g cm−3, ɛ = 0.080 ± 0.049. However, it must be noted that the other solutions cannot be excluded just yet.
12 citations
Spanish National Research Council1, University of Paris2, Federal University of Technology - Paraná3, University of Central Florida4, University of Padua5, INAF6, Aix-Marseille University7, University of Ljubljana8, Institut Polytechnique des Sciences Avancées9, Institut de mécanique céleste et de calcul des éphémérides10, Federal University of Rio de Janeiro11, Max Planck Society12, Sao Paulo State University13, German Aerospace Center14, University of Alicante15, University of Zagreb16, Lawrence Berkeley National Laboratory17, Konkoly Thege Miklós Astronomical Institute18, Eötvös Loránd University19, Slovak Academy of Sciences20, University of Crete21, University of Valencia22, University of La Laguna23
TL;DR: In this article, the authors derived a geometric albedo of 0.147 ± 0.005 for the trans-Neptunian object (TNO) 2002 TC302, which represents the best observed stellar occultation other than Pluto in terms of the number of chords published thus far.
Abstract: Context. Deriving physical properties of trans-Neptunian objects is important for the understanding of our Solar System. This requires observational efforts and the development of techniques suitable for these studies.Aims. Our aim is to characterize the large trans-Neptunian object (TNO) 2002 TC302 .Methods. Stellar occultations offer unique opportunities to determine key physical properties of TNOs. On 28 January 2018, 2002 TC302 occulted a m v ~ 15.3 star with designation 593-005847 in the UCAC4 stellar catalog, corresponding to Gaia source 130957813463146112. Twelve positive occultation chords were obtained from Italy, France, Slovenia, and Switzerland. Also, four negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body can be obtained that is compatible with the near misses.Results. The resulting ellipse has major and minor axes of 543 ± 18 km and 460 ± 11 km, respectively, with a position angle of 3 ± 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5 m telescope at Sierra Nevada Observatory and the 1.23 m telescope at Calar Alto observatory, allows us to derive possible three-dimensional shapes and density estimations for the body based on hydrostatic equilibrium assumptions. The effective diameter in equivalent area is around 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to ~300 km in diameter, which is required to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with absolute magnitude measurements we derive a geometric albedo of 0.147 ± 0.005, which would be somewhat smaller if 2002 TC302 has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere.
9 citations
Federal University of Technology - Paraná1, Institut Polytechnique des Sciences Avancées2, Institut de mécanique céleste et de calcul des éphémérides3, Spanish National Research Council4, Paris Diderot University5, Federal University of Rio de Janeiro6, University of Central Florida7, Sao Paulo State University8, Wellington Management Company9, University of Padua10, INAF11, University of Canterbury12, Academy of Sciences of the Czech Republic13, Aix-Marseille University14, Konkoly Thege Miklós Astronomical Institute15, Eötvös Loránd University16, University of Liège17, Slovak Academy of Sciences18, Adam Mickiewicz University in Poznań19, University of Ljubljana20, Sharif University of Technology21, University of Edinburgh22, University of Antofagasta23
TL;DR: In this article, the authors analyzed data from stellar occultations to obtain astrometric positions of the involved bodies, and derived 37 precise positions for 19 TNOs and 4 Centaurs.
Abstract: Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurated ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability. We analyzed data from stellar occultations to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 catalog is the reference. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respect to the detected chord and the International Celestial Reference System (ICRS) propagated Gaia DR2 star position. We derive 37 precise astrometric positions for 19 TNOs and 4 Centaurs. Twenty-one of these events are presented here for the first time. Although about 68\% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter and shape constraints for a few bodies are also presented as valuable byproducts. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object.
5 citations
Federal University of Rio de Janeiro1, Sao Paulo State University2, Janssen Pharmaceutica3, Michigan Career and Technical Institute4, Institut de mécanique céleste et de calcul des éphémérides5, University of Sydney6, University of Dundee7, National Scientific and Technical Research Council8, National University of La Plata9, Royal Astronomical Society10, University of Liège11, State University of West Paraná12, Sharif University of Technology13, University of Edinburgh14
TL;DR: Gomes junior, A. R., et al. as discussed by the authors, A.R., and A. S. R.. Universidade de Sao Paulo, Brazil, and U.F. do Rio de Janeiro, Brazil
Abstract: Fil: Gomes Junior, A. R.. Universidade de Sao Paulo; Brasil. Universidade Federal do Rio de Janeiro; Brasil. Laboratorio Interinstitucional de e-Astronomia; Brasil
5 citations
Federal University of Technology - Paraná1, Institut de mécanique céleste et de calcul des éphémérides2, Institut Polytechnique des Sciences Avancées3, Spanish National Research Council4, Paris Diderot University5, Federal University of Rio de Janeiro6, University of Central Florida7, Sao Paulo State University8, Wellington Management Company9, INAF10, University of Padua11, University of Canterbury12, Academy of Sciences of the Czech Republic13, Aix-Marseille University14, Konkoly Thege Miklós Astronomical Institute15, Eötvös Loránd University16, University of Liège17, Slovak Academy of Sciences18, Adam Mickiewicz University in Poznań19, University of Ljubljana20, Sharif University of Technology21, University of Antofagasta22
TL;DR: In this paper, the authors analyzed data from various stellar occultation detections to obtain astrometric positions of the involved trans-Neptunian objects and four Centaurs.
Abstract: Context. Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these distant small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape.Aims. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurate ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability.Methods. We analyzed data from various stellar occultation detections to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 stellar catalog is the reference, thus providing accurate positions. Events with detection from one or two different sites (single or double chord) were analyzed to determine the event duration. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respectto the detected chord and the International Celestial Reference System propagated Gaia DR2 star position.Results. We derive 37 precise astrometric positions for 19 TNOs and four Centaurs. Twenty-one of these events are presented here for the first time. Although about 68% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter of bodies such as Sedna, 2002 KX14 , and Echeclus, and also shape constraints on 2002 VE95 , 2003 FF128 , and 2005 TV189 are presented as valuable byproducts.Conclusions. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object, or even the study of topographic features such as satellites or rings.
3 citations
04 Aug 2020
TL;DR: In this article, the authors used the NIMA ephemeris and the PACS/Herschel and MIPS (Spitzer Space Telescope) instruments to obtain a rotational light curve of 2002 MS4 and determined two possible periods (7.33 h and 10.44 h) with low amplitude variation (0.05 +/- 0.01 mag).
Abstract:
Abstract
Transneptunian Objects (TNOs) are the remnants of our planetary system and can retain information about the early stages of the Solar System formation. Stellar occultation is a ground-based method used to study these distant bodies which have been presenting exciting results mainly about their physical properties. The big TNO called 2002 MS4 was discovered by Trujillo, C. A., & Brown, M. E., in 2002 using observations made at the Palomar Observatory (EUA). It is classified as a hot classical TNO, with orbital parameters a = 42 AU, e = 0.139, and i = 17.7º. Using thermal measurements with PACS (Herschel) and MIPS (Spitzer Space Telescope) instruments, Vilenius et al. 2012 obtained a radius of 467 +/- 23.5 km and an albedo of 0.051.
Predictions of stellar occultations by this body in 2019 were obtained using the Gaia DR2 catalogue and NIMA ephemeris (Desmars et al. 2015) and made available in the Lucky Star web page (https://lesia.obspm.fr/lucky-star/). Four events were observed in South America and Canada. The first stellar occultation was detected on 09 July 2019, resulting in two positives and four negatives chords, including a close one which proven to be helpful to constrain the body’s size. This detection also allowed us to obtain a precise astrometric position that was used to update its ephemeris and improve the predictions of the following events. Two of them were detected on 26 July 2019, separated by eight hours. The first event was observed from South America and resulted in three positive detections, while the second, observed from Canada, resulted in a single chord. Another double chord event was observed on 19 August 2019 also from Canada.
Due to its size, it is expected that 2002 MS4 is in hydrostatic equilibrium. Thirouin, A. 2013 obtained a rotational light curve of 2002 MS4 and determined two possible periods (7.33 h and 10.44 h) with low amplitude variation (0.05 +/- 0.01 mag). Admitting that it has a Maclaurin shape, the projected limb in the sky plane for Earth-based observers should be the same in the 09 July and 26 July events. The multi-chord detection allows determining an interval of parameters for size and shape. Considering that the same figure should have been observed in the 09 July event, we could use the both chords and the negative observations to constrain its physical parameters. With that, we could determine that 2002 MS4 has an equivalent radius of 385 +/- 1 km (Figure 1). Our results indicate that this TNO is about 100 km smaller in diameter than the value obtained by Vilenius et al. 2012, implying an albedo of 0.076 (Hv = 4.0 +/- 0.6) . The astrometric positions derived from these data were also helpful to improve forthcoming stellar occultations, in special the one crossing Europe on 08 August this year. More data from stellar occultations and observations of rotational light curves will help to confirm these results and assumptions.
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